Cornalvo Reservoir is located about 10 km from the city of Merida, in the autonomous community of Extremadura, Spain. The capacity of the reservoir is estimated at 11 hm3.1 The dam is a Roman building on the stream Albarregas, which was used to supply water to parts of the city of Emerita Augusta (now Mérida). Containment is a solid wall of 220 m long by 18 m in height, with the part that is in contact with water, as a grandstand. The work is dated to the year 130 A.D.. The designer is unknown. This building was declared a National Monument on December 13, 1912. The reservoir is still used in the actualidad.Todo its surroundings is a natural park, so enjoy special protection of the Board of Extremadura since 1988. It has a rich flora and fauna and at the entrance of the park include an interpretive center that will help us in the visit.